On the ops desk, ETD and ETA frame the schedule a booking is planned against, and the forwarder passes the ETA on in the pre-alert so destination work can start on time. The confusable is estimated versus actual: ETA and ETD are forecasts that shift with weather, congestion, and routing changes as the voyage progresses, while ATA and its departure counterpart ATD (actual time of departure) are recorded events that do not move. The desk plans against the estimates but reconciles milestones and the carrier's free-time clock against actual events rather than forecasts before paying or disputing a charge.
Glossary
ETA vs ETD vs ATA
ETA (estimated time of arrival) and ETD (estimated time of departure) are forecasts of when a shipment will reach the port of discharge or leave the port of loading, while ATA (actual time of arrival) is the recorded time it in fact arrived.